docs: def outputForInput(self, inState, inputSymbol):
          """
          A 2-tuple of (outState, outputSymbols) for inputSymbol.
          """
          for (anInState, anInputSymbol,
               outState, outputSymbols) in self._transitions:
              if (inState, inputSymbol) == (anInState, anInputSymbol):
                  return (outState, list(outputSymbols))
          raise NoTransition(state=inState, symbol=inputSymbol)